The invention relates to a yarn winding apparatus having a yarn traversing system which includes a guide edge and a pair of oppositely rotating blades for respectively moving the yarn in opposite directions along the guide edge. Such a yarn winding apparatus is known, for example, from DE 34 04 303 A1; EP 120 216 A; DE 34 17 457 C2; DE 37 03 731 A1.
In the yarn traversing systems of these yarn winding apparatus, the guide edge has the following function: the yarn entraining arms or rotary blades have a constant angular speed, but have between the stroke ends a different guiding speed in the traversing direction, in which the yarn is to be reciprocated parallel to the package axis. The guiding speed is dependent on the constantly changing angular position of the rotary blades and, therefore, is sinusoidal. The main guide edge deflects the yarn from the traversing plane such that these speed differences are compensated in desired manner. A corresponding configuration of the guide edge allows to accomplish that the traverse speed is constant between the stroke ends--i.e., apart from the short reversal regions, in which the direction of movement is reversed. However, the configuration of the guide edge and the rotary blades also allows to predetermine desired laws of movement. In this connection, the traversing plane is described as the tangential plane which extends through the apex yarn guide and the subsequent rotating cylinder to which the yarn advances. The apex yarn guide is arranged centrically above the traverse stroke. It is spaced apart from the rotating cylinder such that the yarn is able to stand the yarn tension fluctuations which result from the traversing motion. These yarn tension fluctuations result from the fact that the yarn length between the apex yarn guide and rotating body changes continuously, i.e., increases and decreases, as a result of the traversing motion. The rotating body is generally a contact roll, to which the yarn advances, and about which the yarn loops partially, so as to then advance to the package.
Yarn traversing systems of the prior art permit to reciprocate the yarn over a long traverse stroke, for example 250 mm, with only one rotor for each direction of movement. As a result, however, it is necessary to compensate for great differences in the guiding speed. For this reason, the guide edge extends, in particular in the central region of the traverse stroke, far into the traversing plane, whereas it extends in the region of the traverse stroke ends close to the traversing plane. Accordingly, the looping angle of the yarn on the guide edge is large in the central region of the traverse stroke, and accordingly the looping angle of the yarn on the guide edge is small in the region of the stroke ends.
It is the object of the invention to avoid these great differences in the looping angle, which also lead to different yarn tensions, and to thereby enable long traverse strokes.